Explore-a-tree--a terrific brainstorming web tool. This tool goes way beyond simple mind maps. It provides users with multiple brainstorming structures to analyze problems and develop ideas. Easy to use and great for helping students find different--structured--ways to approach a question or problem. Very useful.
think--a mind-maping tool
Bubble-us--color-coded bubbles for making mind maps and other web-type brainstorms.
Pro-Con lists--another way to help students generate ideas about controversial topics
Wisdomaps--brainstorming in a variety of mapping forms. Easy to use and view.
Edistorm--a collaborative brainstorming tool using sticky notes
Some resources for mind-mapping
How to build a mind-map in MS word (very comprehensive; lots of good suggestions)
WiseMapping--
MindMeister--"on-line mind mapping"
Slatebox--Idea mapping with a variety of interesting forms and templates
Cacoo--"A user-friendly collaborative drawing program"; also great for charts
Board800--"A collaborative, multi-user whiteboard program"; another program like this is CoSketch
OneWord--a unique free-writing tool that's good for generating story ideas
WallWisher--a collaborate sticky-note brainstorming space
Popplet--an easy-to-use visual tool for mindmaping and brainstroming
SpiderScribe--a neat combination of mind mapping and collaboration
36 Concept map tools